A bent Laue analyser crystal for Rayleigh-to-Compton computed tomography

Abstract

A new optical system to perform tomography based on the Rayleigh-to-Compton (RC) method with high spatial and spectral resolution is presented. The RC technique allows the effective atomic number of a sample to be measured and finds application in bone mineral densitometry in medicine. It is particularly useful for the characterization of the distribution of biological materials which do not exhibit distinctive diffraction peaks. The system is based on the separation of the elastic line from the spectrum that is scattered by the sample by means of a bent Laue analyser crystal, and the subsequent independent detection of the elastic and inelastic parts of the spectrum with two large-area scintillation counters. The high energy resolution permits operation at low momentum transfer, where the RC method has its best contrast-to-noise ratio for low-Z materials. The geometrical and spectral requirements in terms of the incident beam and the conical analyser crystal are discussed. A first-generation tomographic imaging system (pencil beam, scanned sample) as implemented at the ESRF Compton-Scattering Station ID15B is described. A high-resolution tomographic reconstruction of a bone sample is presented.

A new technique for angle-dispersive powder diffraction using an energy-dispersive setup and synchrotron radiation

“…To overcome the background problem, a Soller slit system can be used, which consists of multiple collimators that are in a radial alignment, centered at the sample (e.g. Yaoita et al, 1997;Schulze & Kleuker, 1998). By oscillating the Soller slits between the sample and the two-dimensional detector, background scattering can be significantly reduced in the ADD patterns thus obtained.…”